Dark diversity in temperate forests of northeastern China: drivers and implications

Understanding the species composition of a community, including those
species present and those absent but potentially able to occur, is vital
for assessing biodiversity changes and informing conservation planning.
Typically, studies focus on observed taxonomic diversity but ignore
undetected species expected to be present based on co-occurrence
patterns—referred to as dark diversity. Dark diversity serves as a
sensitive indicator of biodiversity change, often responding earlier than
observed diversity. However, its underlying drivers, especially
environmental and anthropogenic factors, remain poorly understood in
forest ecosystems. In this study, we quantified both dark and observed
diversity and applied logistic regression to identify traits influencing
species’ likelihood of belonging to dark diversity at the species level.
Variance partitioning and spatial autoregressive models were used to
disentangle the effects of environmental and human drivers at the plot
level. Our results revealed that key traits such as mycorrhizal type,
specific leaf area and tree height determine a species’ likelihood of
belonging to dark diversity, and that dark and observed diversity respond
differently to environmental and anthropogenic factors. Dark diversity was
mainly influenced by the interaction of environmental factors and human
impacts, with annual mean temperature being the strongest environmental
driver. Observed diversity, in contrast, was most influenced by annual
mean precipitation. Dark diversity increased with mean annual temperature,
declined under the combined influence of human footprint and
precipitation, and increased with the interaction between human footprint
and precipitation seasonality. Observed diversity was positively affected
by precipitation and altitude, and negatively influenced by human
footprint-temperature and altitude-roadless area interactions. Our
findings highlight the importance of addressing climate and human
pressures in conservation planning, as dark diversity signals hidden
constraints on species establishment and persistence.